The present invention relates to transportation of cargo and, more particularly, to cargo lashing fittings affixed to the deck of a transportation vehicle.
In the maritime industry, the transportation of cargo requires securing systems and devices that can support and transfer the very high loads experienced as a result of the ship's dynamics and environmental conditions. Ultimate design loads can reach 70,000 pounds for general cargo securing, and can reach 110,200 pounds for container securing. These high loads often dictate that the cargo lashing fitting affixed to the vessel be made of properly designed and treated steel.
As ships are being designed to be lighter, faster and more economical, aluminum structure is becoming more common, including for large commercial and military vessels. This usage of aluminum makes it difficult to design and install a cargo lashing fitting that will handle and properly transfer loads to the ship's structure. First, the housing of the fitting must be compatible with the aluminum deck of the ship, which generally means that the housing must also be aluminum. Second, aluminum is not an ideal material for the securing plate which interfaces with the lashing gear.
More particularly, lashing gear typically includes steel hooks that can gall an aluminum securing plate. In fact, even steel securing plates are subject to galling over time. One known prior art cargo lashing fitting is referred to as a tri-metallic fitting, and is manufactured using an explosion bonding technique which transitions from a steel securing plate to an aluminum housing through a titanium ring. Thus, the fitting provides a steel securing plate for interfacing with the lashing gear, as well as an aluminum housing for welding compatibility with the deck of the ship. However, as will be recognized by those skilled in the art, explosion bonding is a complicated and expensive process.
In addition, the prior art fittings are typically installed as an integrated unit. This means that if a securing plate is damaged and/or requires maintenance, the entire fitting must be “flame cut” out of the deck of the ship. This is, of course, a time consuming and intricate procedure, which can result in shipping delays and/or increased costs. Finally, there may be applications where the preferred securing plate may vary depending on the nature of the mission. In the past, once a fitting was installed in the deck, it generally remained there until removed by flame cutting.
There is therefore a need in the art for a cargo lashing fitting which provides a simple, cost efficient manner of integrating a securing plate within an aluminum housing. There is a further need in the art for a cargo lashing fitting which allows for removal/replacement of the securing plate without flame cutting of the fitting from the deck.